The exposure of cells to intense electric fields for brief periods of time temporarily destabilizes membranes. This effect has been described as a dielectric breakdown due to an induced transmembrane potential, and was termed “electroporation”, or “electropermeabilization”, because it was observed that molecules that do not normally pass through the membrane gain intracellular access after the cells were treated with electric fields. The porated state was noted to be temporary. Typically, cells remain in a destabilized state on the order of minutes after electrical treatment ceases.
Various devices and methods for achieving electroporation have been described, including those of a subset of the present inventors (U.S. Pat. No. 6,135,990) and that of Weaver (U.S. Pat. No. 5,983,131).
Present devices and methods are relatively large-scale, occurring over centimeters, with electrodes placed in a fixed configuration. Two basic electrode types are currently known by those in the art. A first type comprises two flat parallel plates. A second type is formed of two insertable needles. Flat plates are limited in their use as little control over the depth of electric field penetration into tissue is achieved. The two-needle system is also limited as the total volume of tissue treatable with this type of array is limited to a narrow rectangle of tissue between the two needles. Furthermore, needle electrodes are adapted to deliver peak power in the kilowatt range across electrode pairs separated by relatively large distances.
Accordingly, what is needed in the art is an electroporation device that utilizes lower levels of activation energy to minimize tissue damage and patient discomfort.
There is another need in the art for an electroporation device that conforms to three-dimensional in vivo tissue structures.
There is another need in the art for an electroporation device able to perform electromigration of molecules wherein they are coincident to the target tissue.
It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed.
However, in view of the prior art in at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.